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tun: fix a crash bug and a memory leak

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This patch fixes a crash
tun_chr_close -> netdev_run_todo -> tun_free_netdev -> sk_release_kernel ->
sock_release -> iput(SOCK_INODE(sock))
introduced by commit 1ab5ecb90c

The problem is that this socket is embedded in struct tun_struct, it has
no inode, iput is called on invalid inode, which modifies invalid memory
and optionally causes a crash.

sock_release also decrements sockets_in_use, this causes a bug that
"sockets: used" field in /proc/*/net/sockstat keeps on decreasing when
creating and closing tun devices.

This patch introduces a flag SOCK_EXTERNALLY_ALLOCATED that instructs
sock_release to not free the inode and not decrement sockets_in_use,
fixing both memory corruption and sockets_in_use underflow.

It should be backported to 3.3 an 3.4 stabke.

Signed-off-by: Mikulas Patocka <mikulas@artax.karlin.mff.cuni.cz>
Cc: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Mikulas Patocka
2012-07-19 06:13:36 +00:00
committed by David S. Miller
parent 521f549097
commit b09e786bd1
3 changed files with 7 additions and 0 deletions
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include/linux/net.h
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@@ -72,6 +72,7 @@ struct net;
#define SOCK_NOSPACE 2
#define SOCK_PASSCRED 3
#define SOCK_PASSSEC 4
#define SOCK_EXTERNALLY_ALLOCATED 5
#ifndef ARCH_HAS_SOCKET_TYPES
/**